The Sail-Backed Reptile Ctenosauriscus from the Latest Early Triassic of Germany and the Timing and Biogeography of the Early Archosaur Radiation

Background Archosaurs (birds, crocodilians and their extinct relatives including dinosaurs) dominated Mesozoic continental ecosystems from the Late Triassic onwards, and still form a major component of modern ecosystems (>10,000 species). The earliest diverse archosaur faunal assemblages are known from the Middle Triassic (c. 244 Ma), implying that the archosaur radiation began in the Early Triassic (252.3–247.2 Ma). Understanding of this radiation is currently limited by the poor early fossil record of the group in terms of skeletal remains. Methodology/Principal Findings We redescribe the anatomy and stratigraphic position of the type specimen of Ctenosauriscus koeneni (Huene), a sail-backed reptile from the Early Triassic (late Olenekian) Solling Formation of northern Germany that potentially represents the oldest known archosaur. We critically discuss previous biomechanical work on the ‘sail’ of Ctenosauriscus, which is formed by a series of elongated neural spines. In addition, we describe Ctenosauriscus-like postcranial material from the earliest Middle Triassic (early Anisian) Röt Formation of Waldhaus, southwestern Germany. Finally, we review the spatial and temporal distribution of the earliest archosaur fossils and their implications for understanding the dynamics of the archosaur radiation. Conclusions/Significance Comprehensive numerical phylogenetic analyses demonstrate that both Ctenosauriscus and the Waldhaus taxon are members of a monophyletic grouping of poposauroid archosaurs, Ctenosauriscidae, characterised by greatly elongated neural spines in the posterior cervical to anterior caudal vertebrae. The earliest archosaurs, including Ctenosauriscus, appear in the body fossil record just prior to the Olenekian/Anisian boundary (c. 248 Ma), less than 5 million years after the Permian–Triassic mass extinction. These earliest archosaur assemblages are dominated by ctenosauriscids, which were broadly distributed across northern Pangea and which appear to have been the first global radiation of archosaurs

Buntsandstein in the Holy Cross Mountains: chronostratigraphy and lithostratigraphical correlation with the Thuringian Basin

The study was performed to attempt the lithostratigraphic correlation of the Buntsandstein in the margin of Holy Cross Mountains region with that of the Thuringian Basin, and simultaneously, to clarify its position in the chronostratigraphic scheme, basing on biostratigraphic data (microflora, conchostracans), and on the existence of regional discordances. The authors found strong analogies with other Buntsandstein sections of the Europe. On the other hand, because of the position of the studied area within the marginal part of the Central European Basin, Buntsandstein of the Holy Cross Mountains region is developed in different facies, more fluvial, instead of lacustrine ones. The common presence of Conchostraca representing the same species as in other parts of the Central European Basin (Thuringia), enables possible the correlation of the investigated area with the Thuringian Basin, and helps to locate stratigraphic gaps and discordances. The authors found that the lower boundary of the Buntsandstein and the boundary between the Lower and Middle Buntsandstein in the Polish study area are not equivalents of those in other areas. Also note worthy is the presence at the margin of the Holy Cross Mountains of youngest Permian terrigenous deposits not connected with the Zechstein salinar sedimentation, included to date to Zechstein or to Buntsandstein. The key for understanding the lithostratigraphic scheme of the Buntsandstein of Holy Cross Mountains region is an assumption, that the Zagnańsk Formation is mostly of fluvial, instead of lacustrine origin, consisting of equivalents of the whole Lower Buntsandstein, and that of the lower Volpriehausen Formation of the Middle Buntsandstein, with the Volpriehausen discordance present within. Authors also assume, that at least in this case, differences in the marginal part of the sedimentary basin, in comparison with its central part, depend on the presence of fluvial facies instead of lacustrine ones, and onthe presence of sedimentary gaps and discordances whose duration is progressively longer towards the basin margin enlarges in the direction to the basin margin

New finds of vertebrate footprints from the Lower Permian of Wambierzyce, Poland

New specimens of vertebrate footprints are reported from the Early Permian deposits in Poland. Footprints discovered in a well-known Early Permian Rotliegend tracksite at Wambierzyce (old German name Albendorf) represent ichnites of Hyloidichnus arnhardti Haubold, 1973

New site with vertebrate footprints from the Upper Buntsandstein of the Holy Cross Mountains, Central Poland

Vertebrate footprints are abundant in the Buntsandstein of the Holy Cross Mountains (central Poland) and have been documented in numer-ous publications. A new site vertebrate trackside has been discovered in near Suchedniów. Chirotheriidae (Synaptichnium sp., Chirotherium barthii, and Brachychirotherium sp.), Rhynchosauroidae (Rhynchosauroides sp.), and probably amphibian footprints (cf. Capitosauroides sp.) are reported from the lower part of the Upper Buntsandstein Baranów Formation (complex of different fluvial deposits) exposed at Kopulak quarry. Differentiated invertebrate ichnofossils (Cruziana problematica, Scoyenia sp., Palaeophycus sp., Skolithos sp., Lockeia sp., and cf. Gordia sp.) and plant remains have been also found in this site. Three types of vertebrate subaqueous traces (footprints of swimming animals) are identified: (1) swim traces - structures preserved as digits or claws scratches; (2) partially preserved pes or manus imprints; (3) other enigmatic traces -referred to as “problematic forms”

Reptile tracks (Rotodactylus) from the Middle Triassic of the Djurdjura Mountains in Algeria

In 1983, during stratigraphic investigations in the Djurdjura Mountains, vertebrate tracks were discovered in the Middle Triassic Haizer–Akouker Unit at the Belvédčre (Bkherdous) locality in Algeria. The footprints are about 2 cm long and consist of impressions of four clawed digits (I–IV), plus a reverted digit V. Manus imprints were overstepped by those of the pes. Originally interpreted as lizard footprints, they have been recently diagnosed as Rotodactylus cf. bessieri Demathieu 1984. In the current literature, Rotodactylus trackmakers are regarded as a group closest to dinosaurs among stem archosaurs. The footprints demonstrate a terrestrial sedimentary regime in the Maghrebids area during the ?late Anisian